Co-firing of biomass with coal in fluidized bed combustors is a promising alternative which leads to environmentally friendly use of coal by reducing emissions and provides utilization of biomass residues. Therefore, effect of biomass share on gaseous pollutant emissions from fluidized bed co-firing of various biomass fuels with high calorific value coals have extensively been investigated to date. However, effect of co-firing of olive residue, hazelnut shell and cotton residue with low calorific value lignites having high ash and sulfur contents has not been studied in bubbling fluidized bed combustors to date. In this thesis study, co-firing of typical Turkish lignite with olive residue, hazelnut shell and cotton residue in 0.3 MWt METU Atmospheric Bubbling Fluidized Bed Combustion (ABFBC) Test Rig was investigated in terms of combustion and emission performance and ash behavior of different fuel blends. The results reveal that co-firing of olive residue, hazelnut shell and cotton residue with lignite increases the combustion efficiency and freeboard temperatures compared to those of lignite firing with limestone addition only. O2 and CO2 emissions are not found sensitive to increase in olive residue, hazelnut shell and cotton residue share in fuel blend. Co-firing lowers SO2 emissions considerably while increasing CO emissions. Co-firing of olive residue and hazelnut shell has no significant influence on NO emissions, however, reduces N2O emissions. Co-firing cotton residue results in higher NO and N2O emissions. Regarding to major, minor and trace elements partitioning, co-firing lignite with biomasses under consideration shifts the partitioning of these elements from bottom ash to fly ash. No chlorine is detected in both EDX and XRD analyses of the ash deposits. In conclusion, olive residue, hazelnut shell and cotton residue can easily be co-fired with high ash and sulfur containing lignite without agglomeration and fouling problems.

Fluidized bed combustion (FBC) ashes containing significant amount of free CaO and CaSO4 in addition to valuable inorganic acidic oxide ingredients such as SiO2, Fe2O3 and Al2O3 can be utilized as potential raw materials in the production of nonexpansive belite-rich calcium sulfoaluminate cement which is one of the special cement type of sulfoaluminate-belite cements having performance characteristics similar to those of ordinary portland cement besides lower energy requirements and CO2 emissions during manufacturing. Therefore, in this thesis study, possibility of producing non-expansive belite-rich calcium sulfoaluminate cement by adding FBC ashes in various proportions to the raw meal was investigated. For this purpose, a raw meal composed a mixture of limestone, bauxite, gypsum together with 10 wt % bottom ash and 15 wt % baghouse filter ash was prepared. It was sintered in a laboratory scale muffle furnace at temperatures of 1200, 1250 and 1300 &deg / C for various holding times. The results of chemical and mineralogical analysis as well as microscopic examination reveal that FBC ashes have the potential to be used in the raw meal due to the presence of characteristic mineral phases of this type of cements, i.e. yeelimite, larnite, ferrite and anhydrite, in the sample obtained at optimum sintering temperature of 1250 &deg / C for 60 min.

A comprehensive model, previously developed for a rectangular parallelepiped shaped 0.3 MWt circulating fluidized bed combustor (CFBC) fired with high calorific value coal burning in sand and validated against experimental data is adapted to cylindrical configuration and is extended to incorporate NOx formation and reduction reactions and pressure drops around cyclone, downcomer and loop seal. Its predictive accuracy is tested by applying it to the simulation of Middle East Technical University (METU) 150 kWt CFBC burning low calorific value indigenous lignite with high Volatile Matter/Fixed Carbon (VM/FC) ratio in its own ash and comparing its predictions with measurements. Favorable comparisons are obtained between the predicted and measured temperatures, pressure profiles and emissions of gaseous species. Results reveal that predictive accuracy in pressure profile strongly depends on the correlation utilized for entrainment in dilute zone and that accuracy in NO emission requires data on partitioning of coal nitrogen into char-N and volatile-N and is affected significantly by dilute zone oxygen content.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains xii, 121 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 117-119).

Through biomass gasification, biomass can be converted at high temperature to a product gas rich in carbon monoxide, hydrogen, and methane. After cleaning and upgrading, the product gas can be converted to biofuels such as hydrogen; methanol; dimethyl ether; and synthetic diesel, gasoline, and natural gas. Particulate matter (PM) is formed as a contaminant in the gasification process, and the aim of this work was to develop and apply a method for sampling and characterization of PM in the hot product gas.   A particle measurement system consisting of a dilution probe combined in series with a bed of granular activated carbon for tar adsorption was developed, with the aim of extracting a sample of the hot product gas without changing the size distribution and composition of the PM. The mass size distribution and concentration, as well as the morphology and elementary composition, of PM in the size range 10 nm to 10 µm in the product gas from a bubbling fluidized bed (BFB) gasifier, a circulating fluidized bed (CFB) gasifier and an indirect BFB gasifier using various types of biomass as fuel were determined.   All gasifiers and fuels displayed a bimodal particle mass size distribution with a fine mode in the <0.5 µm size range and a coarse mode in the >0.5 µm size range. Compared with the mass concentration of the coarse mode the mass concentration of the fine mode was low from all gasifiers. The evaluation of the results for the fine-mode PM was complicated by condensing potassium chloride for the CFB gasifier when using miscanthus as fuel and by condensing tars for the indirect BFB gasifier when using wood C as fuel. The mass concentration of the coarse-mode PM was higher from the CFB gasifier than from the two BFB gasifiers. The coarse-mode PM from the BFB gasifier when using wood A as fuel was dominated by char. In the CFB gasifier the coarse-mode PM was mainly ash and bed material when using all fuels. The coarse-mode PM from the indirect BFB gasifier when using wood C as fuel was mainly ash.

No description available.

The prime objective of a current research project at the University of Natal is to develop a novel autothermal fluidised bed coal gasifier which is capable of efficiently producing synthesis quality gas (rich in hydrogen and carbon monoxide) from discard of duff coal resources using air and steam as the reactant gases. The development of this gasifier was initially motivated to utilise the ever increasing supply of discard coal in South Africa which represents a significant potential source of energy and currently poses severe environmental pollution hazards caused by spontaneous combustion and wind erosion of the discard coal dumps. Recently, however, the gasifier has been considered for the conversion of more general coal resources in an Integrated Coal Gasification Combined Cycle process (IGCC) for the production of electricity. The knowledge of the kinetics of steam gasification of local coal resources is of vital importance to the design of this gasifier. However, no such kinetic data are available of which the author is aware. This thesis presents the following contributions to the overall knowledge of the gasifier (a) The development of a micro reactor to measure the rate of reaction of the steam gasification of coal-char at temperatures of up to l000oC and pressures up to 5 bar absolute; (b) Kinetic studies using the microreactor on the steam gasification of coal-chars derived from Bosjesspruit and Transvaal Navigation coal samples. The following principal results were obtained with Bosjesspruit coal-char : The rate of steam-char gasification is very sensitive to variations in the temperature of reaction in the range 840°C to 920°C. Neither the rate of steam-char gasification nor the product gas composition are affected by the steam partial pressure in the range 1.8 to 4.8 bar absolute; The concentrations of the H2 and CH4 components of the product gas stream rapidly approached their respective equilibrium compositions, whereas the concentrations of CO and CO2 gradually approach their respective equilibrium compositions during gasification at a rate which is typical of the stoichiometry of the Boudouard reaction. The average product gas composition is independent of the temperature of reaction in the range 840°C to 920°C and is approximately 49% H2, 32% CO, 17% CO2 and 2% CH4 on a molar basis; The steam gasification kinetic data are well described by a fundamental Arrhenius-type volumetric reaction model at (c) temperatures of up to 920°C. The value of the activation energy for the reaction is 146 kJ/gmol, which indicates that the gasification kinetics are controlled by the rates of the chemical reactions (ie. C + H2O = CO + H2 and C + CO2 = 2CO) at temperatures up to 920o C; There are no major differences between the kinetics measured for Bosjesspruit coal-char and those reported in the literature for foreign coal-chars. The experimental results obtained for the steam gasification of char derived from Transvaal Navigation coal show that the concentrations of both the Hz and the CH4 in the product gas stream rapidly attain their respective equilibrium values and remain approximately constant throughout gasification, whereas the concentrations of CO and CO2 gradually approach their respective equilibrium values during the course of gasification and almost attain equilibrium concentrations as the conversion of carbon nears completion. The rate of steam gasification of this char is therefore also controlled by the rate of the Boudouard reaction. The mathematical development of a steady-state, one-dimensional compartment model of the gasifier. The model is also presented in the form of a Fortran 77 computer program which is designed to run on a personal computer. The program is capable of simultaneously solving the overall material and energy balances of the gasifier to a tolerance of l% within 15 minutes when using a microprocessor which operates at 10 Mhz. (d) The gasifier simulation program is currently being used in the design of a pilot scale gasifier which is intended to demonstrate the capability of the process on a continous basis of operation. (e) Experimentation on the air-steam gasification of Bosjesspruit coal using a mini-pilot scale gasifier. These experiments have successfully demonstrated the feasibility of the production of a gas stream which is rich in hydrogen and carbon monoxide. The composition of the product gas stream compares well with the predictions of the simulation model of the gasifier. / Thesis (Ph.D.)-University of Natal, Durban, 1990.

The ever-increasing quantity of by-products generated from burning coal in the production of electricity has brought about the need for new areas of utilization. This study examined the use of FGD gypsum and fluidized bed combustion ash along with Class F fly ash in the production of low-energy, 100% by-product cement blends. The cement blends used the advantageous properties of the by-product materials to create cementing properties rather than energy intensive clinker used in ordinary portland cement. The FGD gypsum was converted to hemihydrate which rapidly hydrated to provide the cement with early strength gains, whilst the fluidized bed combustion ash reacted with the Class F fly ash to form pozzolanic cementitious phases which provided the longer-term compressive strength and possibly resistance to weathering. The rate of compressive strength gains and minimizing detrimental expansion were two properties of particular interest in the study. Chemical admixtures were used to improve the compressive strengths of the cement mortars and decrease their solubility.

Global warming is an unequivocal fact proved by the persistent rise of the average temperature of the earth. IPCC reported that scientists were more than 90 % certain that most of the global warming was caused by increasing concentrations of greenhouse gases (GHG) produced by human activities. One alternative to combat the GHG is to explore technologies for utilizing CO2 already generated by current energy systems and develop methods to convert CO2 into useful combustible gases. Two-step conversion of CO2 with catalysts is one of the most promising methods. Ceria (CeO2) is chosen as the main catalyst for this conversion in the thesis. It releases O2 when it is reduced in a heating process, and then absorbs O2 from CO2 to produce CO when it is re-oxidized in a cooling process. To make the conversion economic, solar power is employed to drive the conversion system. In this thesis, a flexible system with fluidized bed reactors (FBRs) is introduced. The thermogravimetric analysis (TGA) was carried out to examine the performance of ceria during its reduction and oxidation. Subsequently, the exergy analysis was used to evaluate the system’s capability on exporting work. The theoretical fuel to chemical efficiency varied from 4.85 % to 43.2 % for CO2 conversions. To investigate the operation mechanism of the system, a mathematical model was built up for the dynamic simulation of the system. Variables such as temperatures and efficiencies were calculated and recorded for different cases. The optimum working condition was found out to be at 1300 ⁰C for the commercial type of ceria. Finally, an experimental system was set up. The hydrodynamics and heat transfer in the fluidized bed reactor were studied. A CFD model was built up and validated with the experimental trials around 120 ⁰C. The model was then used as a reliable tool for the optimization of the reactor. The entire work in the thesis follows the procedure of developing an engineering system. It forms a solid basis for further improvements of the system to recycle CO2. / <p>QC 20141006</p>

Umeå Energi AB har bestämt att en kontroll av pannverkningsgraden för kraftvärmepannan Dåva 2 skall genomföras. I dagsläget genomförs en beräkning av verkningsgraden månadsvis med den direkta beräkningsmetoden. Resultatet varierar dock kraftigt månad till månad varav en undersökning med indirekt beräkningsmetod är av intresse. Arbetet genomförs för att ge en mer noggrant beräknad verkningsgrad samt utreda förlustfaktorer kopplad till pannan. Då pannverkningsgraden i vanliga fall inte inkluderar rökgaskondensering beräknades också totalverkningsgraden för att ge en mer rättvis bild av pannan samt för att illustrera dess relevans. Arbetet genomfördes för två olika driftsfall, hög och låg last, för att undersöka hur verkningsgraden varierar beroende på driftsfall. Arbetet inleddes genom att studera de standarder som finns inom området för att utreda vilka faktorer som skulle beräknas samt vilka kriterier som skulle följas. Det framgick att en hel del provtagningar och analyser skulle genomföras på bland annat bränsle, aska och rökgaser. Detta krävde i sin tur en noggrann planering varav ett provtagningsschema skapades. Samtliga provtagningar genomfördes vid bägge driftsfallen och proverna skickades på analys, därefter kunde verkningsgraden beräknas. Resultatet tyder på hög totalverkningsgrad med något lägre pannverkningsgrad. Beroende på driftsfall varierar pannverkningsgraden mellan 74% vid hög last och 72% vid låg last. Totalverkningsgraden ligger på 92% vid hög last och 91% vid låg last. Den förlustfaktor som är av störst magnitud är rökgasförluster som beror av rökgasernas fukthalt och temperatur. Rökgasförlusterna varierar mellan 24% till 26% för pannverkningsgraden och 6.6% till 7.2% för totalverkningsgraden. Utöver rökgasförlusterna ligger strålningsförlusterna på runt 0.7% vid bägge driftsfallen. Förbränningsförlusterna är mycket låga och varierar mellan 0.52% och 0.53% vilket i kombination med de låga askförlusterna (0.006%-0.04%) tyder på mycket bra förbränning. På grund av de höga verkningsgraderna framkom inga självklara effektiviseringsåtgärder. Då rökgasförlusterna är de största förlustfaktorerna är därför åtgärder mot dessa av störst betydelse för verkningsgraden. Ett alternativ för att öka verkningsgraden ytterligare är att minska fukthalten på de utgående rökgaserna. De är i dagsläget runt 9% och står för majoriteten av rökgasförlusterna. En sänkning av denna fukthalt kan erhållas genom att sänka temperaturen på rökgaserna och på så vis kondensera mer fukt ur rökgaserna. Detta innebär att temperaturen på kondensatet i rökgaskondenseringsanläggningen måste sänkas, vilket i sin tur innebära att antingen sänka fjärrvärmereturen som kyler kondensatet, alternativt installera en värmepump mellan kondensatet och fjärrvärmereturen. Detta kräver dock en djupare utredning för att fastställa om dessa effektiviseringsåtgärder är genomförbara rent tekniskt samt om de är ekonomiskt försvarbara. / Umeå Energi AB has decided that an evaluation of boiler efficiency should be performed on their CHP-plant Dåva 2. Calculation of the efficiency using the input-output method is currently carried out monthly but the results vary greatly over time whereby an evaluation of the efficiency using the energy balance method was of interest. This was done to give a more accurate efficiency and to evaluate boiler losses. Due to the fact that the boiler efficiency doesn’t usually include flue gas condensation two different efficiency were calculated, boiler efficiency and total efficiency.  The boiler and total efficiency was determined for the CHP during two different loads, high and low. This was done to investigate how the efficiency varies with different loads. The work was initiated by studying the standards in the field of efficiency calculations to evaluate which factors and criteria to be calculated and followed.  It was shown that a lot of samplings and analysis was to be performed which demanded accurate sampling interval. A sampling schedule was therefore constructed to be followed. All sampling was then performed at both loads and the efficiency calculations could begin. The results indicate a high total efficiency with somewhat lower boiler efficiency. The boiler efficiency varied depending on the load by 74% on high load and 72% on low load. The total efficiency was 92% on high load and 91% on low load. The greatest losses were all connected to flue gas losses. Losses like moisture in flue gas or hot dry flue gas. The flue gas losses varied between 24% to 26% for the boiler efficiency and 6.6% to 7.2% for the total efficiency on high and low loads. Besides flue gas losses the next greatest loss is radiation losses, about 0.7% for both high and low loads. Losses due to incomplete combustion were very low and varied between 0.52% and 0.53% for high and low load which in combination with the low ash loses (0.006%-0.04%) indicates very good combustion. Due to the relatively high efficiencies, no obvious solutions for decreased energy losses were found. The greatest energy losses are flue gas losses and a solution to this will influence the efficiency the most. One solution to increase the efficiency is to reduce the moisture content of the flue gas. At this time the moisture content is at 9% and contributes the most to the flue gas losses. Reducing the moisture content can be done by lowering the flue gas temperature. This will increase the amount of moisture that is condensed in the flue gas condenser. To achieve this, the flue gas condensate temperature needs to be decreased. This can be done by either lowering the temperature on the district heating return which is cooling the flue gas condensate or install a heat pump between the flue gas condensate and the district heating return. These solutions require a more in depth analysis to evaluate if this is technically possible and if it is economically viable.